It is a general endeavour in case of most people to spend time of travelling and waiting in a more useful way, getting informed or entertaining. Its traditional means besides newspapers and books are the wide-spread walkman (cassette player with stereo earphones) and the radio walkman (earphones with radio receiver).
In spite of the fact that most popular amusement in the homes preceding reading and listening to radio is watching tv and video, however it has not spread in public vehicles, in streets, etc. Its most important reasons are: screen size of miniaturized tv is too small to enjoy the image: watching small picture for a long time strains the eyes; increasing the picture is limited because of claim of portability, ability to keep it in a pocket, on the other hand the limit that screen held in hands can be maximum in an arm's length. Consequently we increase size of picture in vain; over a certain limit picture seen from a too close distance shows line-structure; screen of tv set held in hands, because of sight, is watched by people standing around, which can be disturbing; at day-light or at strong inner lighting image fades or gets contrastless.
Such an appliance is suitable for solving the problem which: 1) light, 2) small sized, 3) picture appears in a good distance (i.e. 2-3 meters), 4) picture cannot be seen by others, 5) the appliance need not be held in hands, 6) while watching it, the person can see his surroundings free, 7) screen is strongly shaded from outer light, in this way it is perfectly contrasty.
The U.S. Pat. No. 4,310,849 is known (Jan. 12, 1982, Stuart M. Glass, "Stereoscopic video system") which is a stereo image and voice broadcasting unit fixed to the head, where tv pictures of right and left type is forwarded to the left and right eyes by fibreglass optics, voices forwarded to ears by stereo earphones. The appliance can be fixed to the head by head band system. Its disadvantages are: band system is heavy and big, wearing it is uncomfortable and striking, and the band in front of the eyes disturbs looking around, i.e. its wearer can see only tv screen and not the surroundings. Tv mounted into helmet is described in G. V. Mamchev's book "The Stereo Television" (Muszaki Konyvkiado, Budapest - Mir Publishing House, Moscow, 1981, page 58). A special cover is fixed to the forehead part of the viewer's helmet in which two cathode ray tubes are situated almost vertically with looking downwards above the left and right eyes, and viewer sees the two screens through a lense and a mirror. The helmet is heavy and big in this case too, and the cover including the mirrors disables the viewer to see the surroundings free.
The U.S. Pat. No. 4,559,555 has the same operation principle (Dec. 17, 1985, Arnold Schoolman, "Stereoscopic viewing system"), a tv set mounted in a helmet as as described by its FIG. 5-7, arrangement of elements and its disadvantages are similar.
The U.S. Pat. No. 4,706,117 (Nov. 10, 1987, Arnold Schoolman, "Stereo Laser disc viewing system") describes a tv set of various construction fixed to the head. According to its FIG. 6-8 there is a protruding extension is a big closed unit in front of the viewer's eyes, in which there are two built-in objectives, two screens with liquid crystal and two lamps for lighting the screen and the extension is fixed to the head by a head band system. According to appliance described in its FIG. 10 there are two lenses in front of the eyes and beyond them there are two LCD screens. In the cases of appliance mentioned in above patent description, the protruding extension makes possible only watching tv and it totally closes the surroundings and their fixing system are big and uncomfortable.
FRG Patent No. DE 3534162 A1 (Nov. 13, 1986, Wolfgang Andrich, "Tragbarer videomonitor") describes such a non-stereoscopic tv set mounted into a helmet, in which case there is a tv image display on top of viewer's head, its image is projected in the eye by a first lense, a mirror, a second lense and a transparent mirror. Its disadvantage is the big sized helmet and the fact that semi-transparent mirror is an ambiguous solution, as it does not make possible to see either the surroundings or tv image undisturbed way, because both can be seen on the same location projected on each other.
At last mention U.S. Pat. No. 4,636,866 (Dec. 22, 1983, Noburu Hattori, "Personal Liquid Crystal Image Display") which describes a protruding extension constructed as close unit which can be fixed to the head by a helmet. There are one or two LCD screens in the protruding extension seen by viewer through a lense or lenses and mirrors. Disadvantages of the appliance are similar to the previous ones.
To summarize all these, common characteristic feature of known solutions realising tv image display wearable on the head are the relatively big size and weight that makes its wearing on the one hand uncomfortable and tiring, on the other hand wearing such helmets in the streets, in public vehicles, etc. is striking. Possibilities of using them are further limited by the fact that user of this appliance has limited ability to orientate, that is why this appliance can be used for watching tv only under undisturbed circumstances.